Prior art found in both patented and non-patented arenas find the interface between the means for turning a valve to the desired position and the actual part of the valve that controls the flow of fluids is considered to be a valve stem. This stem is subject to both rotational or torsional loads and axially driven loads such as compression or tension loads. Due to the need for rotational movement and the presence of axial loads, sealing devices that are used to prevent the flow of fluid from escaping the valve through the valve stem are circularly formed, as lip or cupped seals are not adapted to axial loads and square or lathe cut sealing rings are not adapted for rotational loads. Current applications include the use of a lubrication placed thereupon the sealing devices in order to facilitate a lower amount of friction turning rotational movement. Without this lubrication, the sealing members would dry out and deteriorate or bind and twist causing excessive elongation decreasing the amount of sealing area and possibly failure if the elongation is beyond the plastic range of the material. Self-lubricating materials have a lubricity molded or processed during it's formation are often used to facilitate a smoother rotational movement. Unfortunately, these sealing members that can have lubricity built-in are often not chemically inert to handle the presence the fluids that are present in the valve.
Another problem with lubrication, whether being built in to the O-ring or applied during the assembly process, is that it introduces a contamination into the system. Due to the contact of the fluids onto the sealing O-Ring, lubrication is transferred away from the O-Ring to the fluid, thereby contaminating the fluid and possibly introduce chemicals that will affect other sealing members in other valves, control devices or other seals.
Due to existing valve design, one needs to disassemble a valve to replace the o-rings as the current valve design contains a shoulder to prevents dislodgement during axial loads. FIG. 2 shows a current state of the art ball valve, where the valve stem is held captive by the valve body itself. This reduces the axial loads associated with pressure differential and reduces the axial loads on the O-rings themselves. Entrance and Exit Flanges in this case are threaded into the valve body. The valve stem itself is inserted into the valve body prior to the introduction of the actual ball and is assembled internally. Replacement of the valve stem O-rings requires the user to completely remove the valve from the piping system and disassemble it in order to reach the actual O-Rings.
Even with the introduction of lubrication to help increase the life of O-ring sealing members, it is the inherent constructional defect that causes O-ring failure. O-rings are able to be elongated, whereby their cross-sectional area is reduce, and placed onto rotational stems. An O-ring should have an optimal compression of approximately 14% of its cross sectional area in it elongated state. This leads to the need of high tolerance machining of the rotational member and the bore into which it is placed, often below 0.002 of an inch. This is also where the inherent constructional defect is highlighted as O-rings that are in an elongated condition have greatly reduced abilities to seal while being subjected to axial loads which are present due to the fluxuations in pressure, temperature and other environmental variables.
Current prior art has shown a variety of sealing methods including one O-ring, two seals or a seal another oring seal. A single O-ring as shown in U.S. Pat. No. 4,54,157 issued to Kawanami on Sep. 10, 1985 is typical of application where a single O-ring is used in sake of economically producing a device which can be mass marketed can be used in certain kinds of applications where adjustment is rarely accomplished. This O-ring is subjected to temperature extremes which will degrade an O-ring causing failure and subjects the O-ring to chemicals which will also degrade the O-ring until failure occurs. Constant use of the device will also lead to premature O-ring failure for the aforementioned reasons. Two O-ring seals are used to extend the life of the O-rings seals but are doomed to eventual premature failure just as single O-rings are for the aforementioned reasons. U.S. Pat. No. 4,566,482 issued to Stunkard on Jan. 28, 1986 shows a typical use of a dual O-Ring based valve. Constant adjusting of the valve, as such operations are typical in HVAC applications, wear unnaturally on the O-rings of circular cross-sections as disclosed in the patent.
Some inventions temper the wear on the O-rings by introduction of a different style of seal to supplement the O-ring. This is shown on U.S. Pat. No. 4,637,421 issued to Stunkard on Jan. 20, 1987, This valve contains a “precision machined conical surface 92” that interfaces with another “precision machined conical surface 84” to create a seal when “pressure actuated in a direction toward the bonnet”. There is also a wedge shaped circular packing that aids in the sealing process. This operation only functions when pressure is applied and will not work in the application where suction forces, caused by rapid pressure loss, such as when a pump is shut down. This is a high precision and costly process that only provides a positive seal when the pressure is sufficient to cause the seal to forcibly come into contact with each other.
What is needed is to have a device whereby O-rings are used that are protected or are isolated from extreme parameters of heat and chemical compositions. It is an object of this invention to produce a valve stem which can be sealed with O-rings of reasonable cost using common materials along with lubrication compounds that can increase the life of O-rings while facilitating a smoother operation of the valve stem with lower torque requirements when subjected by loads of fluid pressure.
What is needed is to reduce the amount of torque necessary to actuate a valve stem, while maintaining a reasonable valve stem height. In this invention, it is recognized that when an O-ring is subjected to unequal side loads, the O-Ring can “bind” in the area of greatest side load causing the O-Ring to fail. It is an object of this invention to create a device whereby the valve stem is pre-positioned using angularly shaped solid wedges, which prior to and during load, will center the valve stem in it's preferred path, whereby allowing the O-Ring not to be subjected to the entire amount of the side, extension or compression loads to be subjected upon the valve stem during normal operations. This pre-load will also reduce the amount of torque necessary as the O-ring will not have the opportunity to bind along the sidewalls causing undue frictional components to the rotational movements.
What is needed is a valve stem that does not rely on O-rings as the method of sealing, yet creating a valve stem that is economically viable. It is a further object of this invention to use pre-loaded wedged packing seals, which will allow for a seal against intrusion of fluid into the valve stem. This seal will also thereby prevent escapement of lubricating compounds into the fluid flow preventing contamination, and allows for the use of more resilient lubricating compounds.
What is needed is a design of the valve stem whereby it can be replaced in the field without complete disassembly of the valve. It is a further object of this invention to create a replaceable valve stem where a minimal amount of tools are necessary and repeatability of adequate seal can be repeated with positive feedback of proper assembly. The presence of a lead-in chamfer which guides the stem into the housing prevents the O-rings from being cut or pinched by the straight sides commonly found.
What is needed is a valve stem can be economically produced without the need for critical tolerancing that causes excessive costs. It is an object of this invention that due to the ability to use materials that are chemically inert in critical areas in shapes conducive to rotational movement, this allows for lower tolerancing of the valve stem components. Due to lower tolerancing, the composition of valve stem materials, having slightly different thermal coefficients, can be replaced into the same valve housing, adapting to different environmental variables.
What is also needed is a valve stem that can seal in both applications where compressional and tensional forces can be exhibited in the piping system. It is an object of this invention to create a device whereby the valve stem has seals that will prevent the intrusion of fluids during periods of increasing pressure or decreasing pressure, where suction or vacuum effect create a tensional force pulling the valve stem down. This device also seals during the side loads experienced by large volumes in fluid flow.
These objects are accomplished by the disclosure and the description herein contained in the patent disclosure.